1. Field of the Invention
The present invention relates to a method for forming a textural structure image of a processed food or a raw material for the processed food. The present invention also relates to a fluorescent dye used for forming a textural structure image of a processed food or a raw material for the processed food.
2. Description of the Related Art
From the earliest times, a variety of foods have been known, and vast amounts of researches are still underway to meet the demand for tasty foods. This is also true for processed foods—particularly for processed foods derived from a grain, and more particularly for secondary processed foods, such as breads, noodles, cooked rice, confectioneries, and a surface layer of tempuras, whose principal raw material is wheat flour or rice, which opens avenues of study and research for providing savory processed foods to be conducted.
For example, since taste perception and oral perception have a great effect on the taste of foods, taste perception and oral perception of foods have been researched. As a result, particularly for secondary processed foods, it has been considered that taste perception and oral perception of foods are greatly affected by what form of starches, proteins, and lipids (that are accepted to be three major nutrients) exist in the foods.
Conventionally, taste perception and oral perception of foods have been evaluated only through sensory testing by professional panels. In recent years, attempts have been made to form an image (textural structure image) showing the textural structure (tissue structure) of a food using various apparatuses and devices, and to determine taste perception from the thus-displayed textural structure. However, observation of textural structure obtained from using such apparatuses and devices does not always yield satisfactory evaluation results because borders between respective components of food are unclear, and obtained images are planar.
For example, in the case of observation using an electron microscope, the textural structure of a specimen is observed by applying an electron beam to the specimen and then detecting the reflected electrons (scanning electron microscopy). This method enables observation of the specimen at very high resolution. However, since this method does not permit staining of the sample, discriminating specific components is difficult, and thus structural analysis of borders between the components is also difficult. In the case of observation through an optical microscope, the textural structure of a specimen is observed after staining specific components of a slice to obtain the specimen. However, this method also provides unclear borders between the respective components. Multi-staining may be performed to improve the clearness of the borders between the specific components. Such a multi-staining improves color segmentation of the specific components. However, discernment of the textural structure remains virtually impossible because staining specificity of the specific components is low, and dyes overlap the specific components (Non-Patent Document 1).
The method for observing a textural structure of a specimen after staining specific components of a specimen by joint use of fluorescence observation and non-fluorescence observation including phase contrast observation, differential interference observation, and the like provides a very clear image in comparison to the conventional method. However, the method is still unsatisfactory in that, for example, it fails to provide clear discernment of intertwined starches, proteins and lipids (Patent Documents 1 and 2).    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2002-323449    Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 2003-294626    Non-Patent Document 1: Food Histology (p. 213˜). Koseikan Co., Ltd., Tadahiko Hoshino and two others, published Jun. 5, 1998